ENGR 4501 NPG Chapter 1 Fall 2023 PDF

Chapter 1 Survey of Nuclear Power Systems Survey the origin and types of nuclear power systems, leads to topics covered in following chapters ENG 4501 – Nuclear Power Generation Nuclear Engineering  Nuclear Notation 235...

Chapter 1 Survey of Nuclear Power Systems Survey the origin and types of nuclear power systems, leads to topics covered in following chapters ENG 4501 – Nuclear Power Generation Nuclear Engineering  Nuclear Notation 235 235 235 U ~ U ~ U ~ U-235 92 143 Means: 235 nucleons (protons + neutrons) 92 atomic number (number of protons) 143 number of neutrons Nuclear Engineering  Introduction Man’s main sources of energy: – Atom (chemical reactions) – Nucleus (nuclear reactions, fusion, fission, radioactive decay) Overall focus: Conversion of nuclear energy to electrical energy Chapter: Review of the origin and types of nuclear power systems Nuclear Engineering  Nuclear Energy Conversion Chemical reactions – two or more atoms combine or separate to form new substances – Sharing or exchanging atoms’ orbital electrons Combustion Digestion – Nuclei of the participating atoms are unaffected – Total mass of the materials entering the reaction undergoes negligible change) Decrease – exothermic reactions Increase – endothermic reactions Nuclear Engineering  Nuclear Energy Conversion Reactions involving the nucleus are named “nuclear reactions” – Changes in the nuclei – Changes in the number of orbital electrons There are many types of nuclear reactions Nuclear reactions that produce energy in a large scale are – Fusion – Fission Nuclear Engineering  Nuclear Energy Conversion Fusion – two or more light nuclei are fused into a heavier type – The new nucleus has a mass slightly less the sum of the masses of the original nuclei Fission – a relatively heavy nucleus is fissioned or split into two or more light nuclei – The mass of the products is less than that of the original nucleus Nuclear Engineering  Nuclear Energy Conversion Radioactive decay of radionuclides can be used as a source of energy (e.g., Pu batteries) Radioisotopes – Natural – Artificial (e.g., fission products or neutron irradiation) Nuclear Engineering  Nuclear Energy Conversion Type of Reaction Energy (MeV) Chemical 3-4 x 10-6 Fusion 3-18 Fission 200 Radioactivity 1-5 1 MeV= 1.602 x 10-13 J Nuclear Engineering  Nuclear Energy Conversion Three ways nuclear energy is converted to electrical energy: Single Step (Specialized uses) – Direct collection devices (e.g., nuclear batteries) Two Steps (Specialized uses) – Nuclear to thermal by fusion/fission – From thermal to electrical by thermoelectricity or thermionics (electrons emitted from a substance at very high temperature) Three Steps (Produces largest power) – Nuclear to thermal by fusion/fission – Thermal to kinetic by thermal expansion of heated fluid in a turbine – From kinetic to electrical by an electrical generator Nuclear Engineering  Energy from Nuclear Fusion In the sun and stars, the nuclear reactions are essentially those in which four nuclei of hydrogen fuse to form one helium nucleus 4 11H → 42He + 2 β+ p → n + β+ +ν These reactions are called thermonuclear because extremely high temperatures are required to trigger them Nuclear Engineering  Energy from Nuclear Fusion Man-made fusion is accomplished by fusing two, instead of four nuclei – Much greater probability of two nuclei colliding than of four – 4-hydrogen collisions required billions of years – A D-D reaction required a fraction of a second Note: Deuterium (D) = 2H, Tritium (T) = 3H Natural waters contain about 1 of 6,666 of heavy water (D2O) – Deuterium is plentiful and can supply large amounts of energy Nuclear Engineering  Energy from Nuclear Fusion To accomplish fusion: – High temperatures (108 – 109 oK) Increase kinetic energy Minimize repulsive forces between positive nuclei Create plasma – Plasma density ~ 1015 ions/cm3 – Confinement time ~ tenths of a second Nuclear Engineering Energy from Nuclear Fusion http://www.wikipedia.org/ Nuclear Engineering The Fusion Reactor http://www.wikipedia.org/ Nuclear Engineering The Fusion Reactor Nuclear Engineering  Energy from Nuclear Fission Fission: Caused by a neutron striking a heavy nucleus and releasing two or three more neutrons, starting a chain reaction – Other particles can also cause fission (e.g., gamma rays) Fertile Materials: U-238 and Th-232 are found in nature – Fissionable materials are manufactured from fertile materials Fissionable Isotopes: U-235, Pu-239, and U-233 specifically - U-235 found in natural Uranium (often enriched) - Pu-239 manufactured from U-238 - U-233 manufactured from Th-232 Nuclear Engineering  Energy from Nuclear Fission “Fissionable material: A nuclide that is capable of undergoing fission after capturing either high-energy (fast) neutrons or low-energy thermal (slow) neutrons.” (NRC website) “Although formerly used as a synonym for fissile material, fissionable materials also include those (such as uranium-238) that can be fissioned only with high-energy neutrons.” (NRC website) “As a result, fissile materials (such as uranium-235) are a subset of fissionable materials.” (NRC website) Nuclear Engineering Energy from Nuclear Fission http://www.solcomhouse.com/nuclear.htm Nuclear Engineering  Energy from Nuclear Fission Fission Fragments: Neutron hits fissionable nucleus and causes it to split into two (or more) lighter nuclei not of equal mass, called fragments Fission Products: Include fission fragments and isotopes from radioactive decay of fission fragments. Barium and Krypton are fission fragments, two neutrons are also ejected Complete fission of U-235 is impossible due to fission products capturing neutrons, ending the chain reaction Nuclear Engineering  Energy from Nuclear Fission Fuel: Defined as all U, Pu, and Th isotopes, not including alloying or other chemical compounds in fuel charge Poisoned Fuel: When fissionable nuclei has been consumed (less than 1%). It can be reprocessed for future use Fuel Burnup: Capability of fuel mass to produce energy (Measured as MW-day/ton) Fuel Material: All components of the fuel (chemical, alloy, or mixture used, but not cladding or other structural materials) Nuclear Engineering http://www.science.uwaterloo.ca/ Nuclear Engineering Energy from Nuclear Fission http://www.world-nuclear.org/ Nuclear Engineering  The Chain Reaction Fission Neutrons: Neutrons gained during fission. Essential to chain reactions within the nuclear reactor For U-235, the average amount of fission neutrons is 2.47 Critical Size: Core size to sustain chain reaction of neutrons Critical Mass: Mass of fuel in a core at, or above, critical size Nuclear Engineering  The Chain Reaction Fission neutrons can be extinguished in the following ways: 1) Non-fission capture/absorption by fission products, fuel, structural material, coolant, moderator, etc. 2) Neutrons can escape, or “leak”, from the core. Size matters for core Nuclear Engineering Neutron Energies and Moderation Neutron speeds average 1/10 speed of light and have high kinetic energies. Neutrons are labeled as “fast”, “intermediate”, or “slow”. Moderators: Reduce the speed of neutrons to obtain fission. Water, heavy water, graphite, and beryllium are the most practical and most used. Slow neutrons (“thermal neutrons ~ 0.025 eV”) are thermalized upon reentry from the moderator and are ideal for fissioning/colliding with nuclei of the fuel. Reactors dependent on thermal neutrons are called “Thermal reactors” Fast Reactors: highly enriched fuel and contain no moderators. Benefits from fast neutrons (> 10 keV) Nuclear Engineering Neutron Energies and Moderation Natural uranium – 0.005% U-234 – 0.7% U-235 – 99.3% U-238 Enriched uranium (power production) – Less than 5% U-235 Enriched uranium (education/research) – About 90% U-235 (no longer after 9/11) Nuclear Engineering  Conversion and Breeding Converter – A reactor in which fissionable nuclei, different from those in the original core loading, are produced Breeder – A reactor where more fissionable nuclei are produced than are consumed by fission Nuclear Engineering  Conversion and Breeding Non-fission capture of neutrons by U-238 results in fissionable Pu-239 Nuclear Engineering Th-232 converts to U-233 Nuclear Engineering  Fission Power Plants (A) Liquid Cooled (i) PWR : Pressurized Water Reactor (ii) OMCR : Organic Moderated/Cooled Reactor (iii) LMCR : Liquid Metal Cooled Reactor (iv) BWR : Boiling Water Reactor (B) Gas Cooled (i) Closed Indirect Cycle (ii) Direct Open Cycle (iii) Direct Closed Cycle (C) Fluid Filled (i) LMFR : Liquid Metal Fueled Reactor (1) Liquid Suspension (2) Dust-Carrying Gas Nuclear Engineering Fission Power Plants Liquid-Cooled Reactor www.wikipedia.org Nuclear Engineering Fission Power Plants Graphite Gas Reactor (GCR) http://www.i15.p.lodz.pl/strony/EIC/res/index.html Nuclear Engineering Fission Power Plants Sodium-cooled Fast Reactor www.wikipedia.org Nuclear Engineering Fission Power Plants www.wikipedia.org Nuclear Engineering Type Coolant Description Advantages Disadvantages - Uses H20 as coolant and - Safe, easy to handle - High vapor pressure moderator - Known properties of - Expensive - Pressure in primary loop H20 components about 2200 psia, - H20 abundant, low cost - H20 is corrosive at PWR secondary loop about - Short-lived radiations high T 900 psia - H20 absorbs neutrons - Uses organic liquid - Low pressure, low cost - Decomposes at high T (i.e., tephenyls - a group in components - Requires cleaning up of closely related - Not corrosive systems OMCR aromatic hydrocarbons), - Well known handling - Not universally which is also used as a properties available and moderator expensive Nuclear Engineering Type Coolant Description Advantages Disadvantages - Uses liquid metal (i.e., - Very low vapor - Very corrosive Molten Sodium) pressures - Expensive - Intermediate loop - Excellent heat transfer components and separates primary from properties handling techniques LMCR secondary - Used in fast reactors - Oxidation - Two heat exchangers - Resistance to radiation - Not universally - Graphite/Heavy H20 damage available used as moderator - Boiling of coolant - High heat transfer - Moderator density (H20) in reactor and rates per pound of changes within vapor produced can be coolant reactor leading to BWR used as working-fluid - One loop design nuclear and to turn turbine - Shares advantages of hydrodynamic PWR problems - Shares disadvantages of PWR Nuclear Engineering Type Coolant Description Advantages Disadvantages - Similar to Brayton - Safe, easy to handle - Poor heat transfer Closed Cycle but reactor is - Widely available properties Indirect substituted for - Operates at High T - Requires greater Cycle combustion which correlates to pumping power and chamber high thermal larger air ducts than - Air is coolant efficiency a liquid cooled - Similar to Brayton - Does not absorb large reactor Direct Cycle but reactor is amounts of neutrons - Finned or specially Open substituted for designed fuel Cycle combustion elements raise costs chamber to increase heat- - Air is coolant removal rates - Gas circulates Direct entire plant Closed - Heat rejection can Cycle be air and/or H20 - Coolant can be He Nuclear Engineering